This invention relates generally to the field of locks of the so-called multiple axial pin tumbler type, commonly referred to in the art as an "ace type" lock, having means for preventing axial movement of the tumbler pins when an attempt is made to pick the lock by a process known as "torquing". A typical example of this type of lock is disclosed in U.S. Pat. No. 3,681,955 granted Aug. 18, 1972 to Ronald F. Sturgens. The construction includes a housing containing relatively fixed and movable cylinders, each containing portions of the usual split pins or tumblers. The tumblers are provided with grooves which are engaged by restricted portions of the bores in the fixed cylinder in which they are slidably disposed when an attempt is made to pick the lock, thus preventing further movement necessary to find the parting line of each tumbler and align it with the plane of abutment of the relatively fixed and movable cylinders. While the construction disclosed in the above mentioned patent is quite effective, at least one of the fixed and movable cylinders must be provided with a plurality of bores of given diameter and counterbores of lesser diameter, a complicated machining operation tending to increase the cost of production. This structure is required in a part of the lock which is not readily manufactured by die casting techniques, and owing to the usual small size of the fixed cylinder, machining operations are not easily performed.